<?php
	//1.将timestamp,nonce,token按字典排序
		$timestamp = $_GET['timestamp'];
		$nonce     = $_GET['nonce'];
		$token     = 'chanmao';
		$signature = $_GET['signature'];
		$array     = array($timestamp ,$nonce,$token);
		sort( $array );
	//2.将排序后的三个参数拼接之后用sha1加密;
		$tmpstr = implode('', $array);
		$tmpstr = sha1($tmpstr);
	//3.将加密后的字符串与signature进行对比,判断该请求是否来自微信
		if ($tmpstr == $signature) {
			# code...
			echo $_GET['echostr'];
			exit;
		}

?>